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We read with interest the manuscript by Kubo et al. (1) comparing vascular response after sirolimus-eluting stenting between patients with unstable and stable angina by optical coherence tomography (OCT). We agree with the authors regarding the contribution of OCT when post-stenting angiography proves ambiguous.

In the drug-eluting stent era, stent under-expansion remains a major predictor of subacute thrombosis and restenosis. Stent under-expansion is often underestimated by coronary angiography, especially with the smallest stent sizes. Previous studies showed the efficiency of intravascular ultrasound (IVUS) in the assessment of stent expansion. Furthermore, IVUS established a relationship between minimum stent area and a lower restenosis rate. We here report a case of drug-eluting stent restenosis linked to an initial under-expansion not diagnosed on angiography. OCT was performed to explain the mechanism of the restenosis and help in its management.

The OCT showed uniform neointimal proliferation in the stent without any uncovered struts (Fig. 1, panel Ax). It clearly diagnosed under-expansion of the stent against a calcified ring (Fig. 1, panel Ay), which was present upstream of the stent (Fig. 1, panel Az).

Angioplasty was performed with a noncompliant balloon (3 × 12 mm at 12 atm). The angiographic result seemed to be perfect (Fig. 1, panel B).

However, the OCT imaging demonstrated proximal stent rupture (Fig. 1, panel By) and the effect of balloon trauma on the neointima of the restenosis that is now shredded and split within the stent. The OCT diagnosed a coronary dissection extending upstream of the stent (Fig. 1, panel Bz). It did not reveal any modification in the distal segment of the stent (Fig. 1, panel Bx).

A new zotarolimus-eluting stent (3 × 18 mm) was then deployed, covering the dissection, and the good angiographic result was confirmed by OCT imaging (Fig. 1, panel C).

In this case, we would like to emphasize the successful use of OCT imaging to diagnose an under-expansion, to show the effect balloon trauma on the neointima, and to evaluate the result of a corrective intervention with more confidence than with angiography alone. Furthermore this observation emphasizes that the angiogram could be insufficient to accurately assess intrastent restenosis or post-intrastent restenosis treatment. Even IVUS rarely shows what OCT would about what happens to the neointima.